How we can execute a javascript function and get a return value in our android application?
Solution 1
you can use mWebView.loadUrl("javascript:checkName"); to call the method...
Then you can use addJavascriptInterface() to add a Java object to the Javascript environment. Have your Java script call a method on that Java object to supply its "return value".
EDIT1: Or you can use following hack:
Add this Client to your WebView:
final class MyWebChromeClient extends WebChromeClient {
@Override
public boolean onJsAlert(WebView view, String url, String message, JsResult result) {
Log.d("LogTag", message);
result.confirm();
return true;
}
}
Now in your java script call do:
webView.loadUrl("javascript:alert(functionThatReturnsSomething)");
Now in the onJsAlert call "message" will contain the returned value.
Edit2:
So it does not work if we call javascript method just after call to load the URL since the page loads take time. So I created a test program to test that...
Following is my html file (named test.html) store in the assets folder:
<html>
<head>
<script language="javascript">
function fieldsOnDelete(message) {
alert("i am called with " + message);
window.myjava.returnValue(message + " JIJO");
}
</script>
<title>iSales android</title>
</head>
<body></body>
</html>
</body>
</html>
Following is my java class that would get that i would add to java script as interface and it would receive the return value:
public class MyJS {
public void returnValue(String string){
Log.d(this.getClass().getSimpleName(), string);
}
}
And following is my activity class:
public class CheckWebView extends Activity {
private WebView webView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_check_web_view);
webView = (WebView) findViewById(R.id.webview);
webView.setWebChromeClient(new WebChromeClient() {
@Override
public void onConsoleMessage(String message, int lineNumber,
String sourceID) {
super.onConsoleMessage(message, lineNumber, sourceID);
Log.d(this.getClass().getCanonicalName(), "message " + message
+ " :::line number " + lineNumber + " :::source id "
+ sourceID);
}
@Override
public boolean onConsoleMessage(ConsoleMessage consoleMessage) {
// TODO Auto-generated method stub
onConsoleMessage(consoleMessage.message(),
consoleMessage.lineNumber(), consoleMessage.sourceId());
Log.d(this.getClass().getCanonicalName(), "message::::: "
+ consoleMessage.message());
return super.onConsoleMessage(consoleMessage);
}
});
webView.addJavascriptInterface(new MyJS(), "myjava");
webView.getSettings().setJavaScriptEnabled(true);
webView.getSettings().setPluginsEnabled(true);
webView.getSettings().setAllowFileAccess(true);
webView.loadUrl("file:///android_asset/test.html");
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_check_web_view, menu);
return true;
}
/* (non-Javadoc)
* @see android.app.Activity#onOptionsItemSelected(android.view.MenuItem)
*/
@Override
public boolean onOptionsItemSelected(MenuItem item) {
webView.loadUrl("javascript:fieldsOnDelete('name');");
return super.onOptionsItemSelected(item);
}
}
The key here is that there should be some time interval between the call to load html file from assets folder and the call to javascript:method. Here I am calling it from onOptionsItemSelected and it is working fine.. if I move the webView.loadUrl("javascript:fieldsOnDelete('name');"); to the end of the onCreate() method the it shows the error that it can not find fieldsOnDelete() method...
Hope it Helps...
EDIT3:
Replace following in your code
webView.loadUrl("javascript:alert(javascript:fieldsOnDelete())");
with
webView.loadUrl("javascript:alert(fieldsOnDelete())");
and try...
Solution 2
In Android KitKat there is a new method evaluateJavascript that has a callback for a return value. The callback returns a JSON value, object or array depending on what you return.
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
// In KitKat+ you should use the evaluateJavascript method
mWebView.evaluateJavascript(javascript, new ValueCallback<String>() {
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
@Override
public void onReceiveValue(String s) {
JsonReader reader = new JsonReader(new StringReader(s));
// Must set lenient to parse single values
reader.setLenient(true);
try {
if(reader.peek() != JsonToken.NULL) {
if(reader.peek() == JsonToken.STRING) {
String msg = reader.nextString();
if(msg != null) {
Toast.makeText(getApplicationContext(), msg, Toast.LENGTH_LONG).show();
}
}
}
} catch (IOException e) {
Log.e("TAG", "MainActivity: IOException", e);
} finally {
try {
reader.close();
} catch (IOException e) {
// NOOP
}
}
}
});
}
You can see a full example here: https://github.com/GoogleChrome/chromium-webview-samples/tree/master/jsinterface-example
Admin
Updated on June 09, 2022Comments
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Admin almost 2 years
How we can execute a javascript function and get a return value in our android appplication ?
We want to execute a javascript on a button press event, we need to pass parameters to the script and get return values, So we are using "WebChromeClient" to implement this, But we got Exception is "SyntaxError: Parse error at undefined:1"
Following is my code
import android.app.Activity; import android.os.Bundle; import android.util.Log; import android.view.View; import android.widget.Button; import android.webkit.JsResult; import android.webkit.WebChromeClient; import android.webkit.WebSettings; import android.webkit.WebView; public class FirstTab extends Activity { private WebView webView; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.regis); try{ webView = (WebView) findViewById(R.id.webView1); webView.getSettings().setJavaScriptEnabled(true); webView.setWebChromeClient(new MyWebChromeClient()); String customHtml = "<html><head><title>iSales</title><script type=\"text/javascript\"> function fieldsOnDelete(){ var x=123; return \"JIJO\"; } </script></head><body>hi</body></html>"; webView.loadData(customHtml, "text/html","UTF-8"); }catch(Exception e) { Log.v("JAC LOG",e.toString()); } } public void onResume() { super.onResume(); final Button button = (Button) findViewById(R.id.button1); button.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { try{ webView.loadUrl("javascript:alert(javascript:fieldsOnDelete())"); } catch(Exception e) { Log.v("JAC LOG",e.toString()); } } }); } final class MyWebChromeClient extends WebChromeClient { @Override public boolean onJsAlert(WebView view, String url, String message, JsResult result) { Log.v("LogTag", message); result.confirm(); return true; } } }